Copy vs move
Copy duplicates entries to another day and time, leaving the originals in place — for eating the same thing again. Move relocates them — for food that was logged to the wrong time or day.
Copying a whole meal
From a meal's header menu, choose Copy meal, pick the destination day and time, and every entry in that meal is duplicated there — with the exact servings and units of the original.
Copying or moving a selection
Long-press to start selecting, mark any combination of entries (across meals, if you want), and use Copy or Move from the selection bar. The same destination picker appears; confirm and you're done.
Copies are faithful: the serving snapshot travels, and an entry logged from a photo keeps its photo attached.
A habit worth knowing
There's no single "repeat yesterday" button — but copying yesterday's biggest meal into today, then adjusting one or two entries, is usually faster than re-logging. And for a meal you copy week after week, saving it as a meal turns it into one tap forever.